The environmental group 350.org, spearheaded by American green activist Bill McKibben, has issued a canny challenge to John McCain and Barack Obama: come to the UN's next round of talks on global carbon emissions reductions, to be held this December in Poznan, Poland.

McCain and Obama have both proclaimed themselves supportive of a global agreement to combat climate change during next year's Copenhagen conference, to which the Poznan talks serve as a prelude of sorts. If one -- or both -- promise to travel to Poland as the president-elect, it would send a strong signal to neighbouring nations that the next US president will get serious about reducing emissions, as 350.org sees it.

The video accompanying the invite is cleverly done, but the trick will be getting either candidate to address the Poznan talks specifically during a week still dominated by the floundering economy.